Apparatus for the recovery of gas dissolved in flue condensate

Abstract

An apparatus and process for separating a more volatile substance from a liquid in which it is dissolved by vacuum means. The apparatus has a perforated inner casing having a plurality of sub-stages which contain packing material to provide a tortuous path of interstices for the liquid to flow through; an outer casing surrounds the inner casing to define an evacuating space between the outer and inner casing and vacuum means to create a vacuum in the evacuating space which communicates with the sub-stages through the perforations in the inner casing. The vacuum means also acts to pull off the more volatile substance.

I claim: 
     
       1. An apparatus for separating a more volatile substnce from a liquid in which it is dissolved, comprising: (a) a substantially gas tight outer shell defining the outer wall of an evacuating space;   (b) an inner shell disposed within said outer shell and defining the inner wall of said evacuatiing space, said inner shell further defining an inner space;   (c) refrigeration conduit means comprising a tube for containing a refrigerant disposed outside of and in thermally conducting relation with said outer shell and means for supplying refrigerant to said conduit at a temperature and a rate such that said outer shell is maintained at a temperature suitable for condensing gas withdrawn from within said inner shell;   (d) sized packing material disposed within said inner shell providing a tortuous path of interstices;   (e) means to introduce a more volatile substance and a liquid in which it is dissolved into the uppermost portion of said inner shell from outside said outer shell;   (f) vacuum means communicating with said evacuating space for withdrawing gas from said space at a rate such that the gas pressure over the liquid in said inner space is controllted to be below atmospheric pressure, to separate the more volatile substance from the liquid by vacuum distillation   (g) means for simultaneously removing the more volatile substance from within said evacuating space, and the liquid from the lowermost portion of the inner space; and   (h) perforated dividing plates disposed within and sealed to the inner shell, positioned transversely to the axis of the outer shell and spaced from one another to divide the inner space into a plurality of vertically spaced successive substages, said packing material disposed on said plates;   a plurality of openings being formed in said inner shell extending between the substages defined by the dividing plates and the evacuating space, the size and number of said openings varying successively from one substage to the next, the rate of withdrawal of gas from said evacuating space, and the size and number of said openings in each substage being such that the gas pressure in each of the substages varies progressively from a maximum value at the uppermost of the substages to a minimum value in the lowermost of the substages, and whereby substantially equal volumes of the volatile substance are withdrawn from each substage.   
     
     
       2. The apparatus according to claim 1 wherein: (a) the outer shell is cylindrical and defines an axis which is vertical.   
     
     
       3. The apparatus according to claim 2 further comprising: (a) means for removing the liquid after treatment.   
     
     
       4. The apparatus according to claim 3 wherein: (a) the evacuating space is divided into at least two stages; and   (b) said vacuum means evacuates each of the stages to a different pressure below atmospheric pressure.   
     
     
       5. The apparatus according to claim 4 wherein: (a) there are two stages, the first evacuated to a first pressure and the second evacuated to a second pressure; and   (b) the vacuum means comprises two vacuum pumps, the first communicating with the first stage to evacuate said first stage and the second communicating with the second stage to evacuate the second stage.   
     
     
       6. The apparatus according to claim 4 wherein: (a) each stage of the evacuating space communicates with at least two substages.   
     
     
       7. The apparatus according to claim 5 wherein: (a) said first pressure is substantially 7 psia;   (b) said second pressure is substantially 1 psia.   
     
     
       8. The apparatus according to any one of the claims 1-7 wherein: (a) the size packing material is comprised of smaller material and larger material.   
     
     
       9. The apparatus according to any one of the claims 4-76 wherein: (a) the sized packing material is comprised of smaller material and larger material; and   (b) the smaller material is positioned closer to the perforated dividing plates at the bottom of each substage.   
     
     
       10. The apparatus according to claim 1 further including: (a) means for returning the liquid condensed on the shell to the inner space.   
     
     
       11. An apparatus for separating a more volatile substance from a liquid in which it is dissolved comprising: (a) a substantially gas-tight outer shell having a vertical axis and defining an outer wall of an evacuating space;   (b) a plurality of down pipes, having axial passages, positioned within the outer shell to provide a plurality of discrete passages for conducting the liquid downward therethrough, having perforations which allow the passages of the down pipes to communicate with the evacuating space;   (c) a helical raceway disposed within each down pipe to provide a helical path for the liquid as it flows downward therethrough;   (d) means communicating with a first end of said outer casing to introduce the volatile substance and liquid to be separated; and   (e) vacuum means communicating with said evacuating space for reducing and maintaining the pressure therein below atmospheric pressure and thereby reducing and maintaining the pressure in the down pipes below atmospheric to cause vacuum distillation of the more volatile substance to separate it from the liquid; and.,   (f) means for simultaneously removing the volatile substance.   
     
     
       12. The apparatus according to claim 11 further including: (a) exit means for removing the liquid after treatment.   
     
     
       13. The apparatus according to claim 12 wherein: (a) the helical raceways have a steeper inclination at the top of the down pipe than at the bottom.   
     
     
       14. The apparatus according to claim 13 wherein: (a) the helical raceway is restricted to an annular portion of the passage of the down pipe to provide an open passage in the center of the down pipe for the volatile substance.